Abnormal Hyperphosphorylation of Tau in Canine Immune-mediated Meningoencephalitis

Background/Aim: Tau is a microtubule-associated protein involved in the assembly and stabilization of microtubules. In human medicine, hyperphosphorylation of tau is associated with microtubule instability and is considered to play a role in the progression of multiple sclerosis (MS). MS is an autoimmune neurological disease that shares many characteristics, including pathological mechanisms, with canine meningoencephalitis of unknown etiology (MUE). With this background, this study investigated the presence of hyperphosphorylated tau in dogs with MUE and experimental autoimmune encephalomyelitis (EAE). Materials and Methods: In total, eight brain samples were examined from two neurologically normal dogs, three dogs with MUE, and three canine EAE models. Anti-(phosphoS396) tau antibody was used for immunohisto-chemistry, which stained hyperphosphorylated tau. Results: In normal brain tissues, hyperphosphorylated tau was not found. In all the dogs with EAE and one of the dogs with MUE, immunoreactivity for S396 p-tau was observed in glial cell cytoplasm and the background in the periphery of the inflammatory lesion. Conclusion: These results suggest for the first time that tau pathology may be involved in the progression of neuroinflammation in dogs, similar to that in human MS.